The invention relates to a pressure regulating device with a pressure regulating valve which has a valve casing with a primary port for the supply of pressure medium, a pressure-regulated secondary port for connection to a load, and a vent port, wherein there is provided between the secondary port and the primary port a first overflow port bordered by a first valve seat and a second overflow port bordered by a second valve seat, wherein a first closing member with a spring bias in the direction of a closed position abutting the first valve seat lies opposite the first valve seat, and a second closing member with a spring bias in the direction of a closed position abutting the second valve seat lies opposite the second valve seat, wherein both closing members belong to a regulating unit which is movable relative to the valve casing, which also contains an actuation element which is movable relative to the two closing members and may be driven under the influence of a control pressure to a regulating movement relative to the valve casing, by means of which each closing member may be moved into at least one open position lifted from the assigned valve seat.
The invention also relates to a method for the operation of such a pressure regulating device.
A pressure regulating device of this kind is known from EP 0 726 511 B1. The core element of this pressure regulating device is a proportionally actuable pressure regulating valve with a regulating unit movable relative to a valve casing and containing a plunger-like actuation element and two closing members resting on the former and movable relative to the actuation element. Each closing member is biased by a spring device towards a closed position in contact with an opposing valve seat, wherein a first valve seat borders a first overflow port running between a primary port and a secondary port, and a second valve seat borders a second overflow port connecting the secondary port to a vent port. In operation of the pressure regulating device, a fluidic pressure medium under a primary pressure is present at the primary port and may be output to a load at the secondary port with a controllable secondary pressure. The level of the secondary pressure may be regulated at a constant pressure value by the positioning of the regulating unit, with the possibility of using a control pressure to act on the actuation element so that the latter executes a regulating movement in the course of which it provides for movement of the two closing members into either a closed position in which the assigned overflow port is closed or into one or more open positions lifted from the assigned valve seat and thereby opening the assigned overflow port for a pressure medium flowing through it.
If in the case of the known valve a malfunction occurs, which prevents an essentially desired closing of the first closing member controlling the connection between the primary port and the secondary port, this may lead to functional impairment or even to hazardous situations with a load connected on the secondary side.